1. Field of the Invention
The present invention relates to a video output apparatus and output video changeover control method used for a moving image digital transmission apparatus and storage apparatus.
2. Description of the Related Art
With the increasing level of integration of communication terminal apparatuses, etc. in recent years, a plurality of video output means (signal sources) such as a camera and circuit for processing stored video data are mounted on a single apparatus. Since such an apparatus having a plurality of signal sources is normally provided with only one display apparatus such as an LCD (liquid crystal display) panel, signals from a plurality of signal sources are switched and displayed as appropriate. That is, in the above apparatus, a plurality of signal sources is configured to share one display means. A signal source normally outputs a set of a video signal and sync signal.
When an apparatus having such a plurality of signal sources switches between those signal sources, sync signals are sometimes not output to a display apparatus at fixed intervals, which results in a problem of causing disturbance on images displayed until sync signals and video signals become stable, giving the user unpleasant impression.
A technology to reduce this disturbance of images displayed is disclosed in the Unexamined Japanese Patent Publication No.HEI 7-134577 (hereinafter referred to as “conventional example 1”) as a “Display apparatus”. When images displayed are switched by a changeover between signal sources, etc., the display apparatus described in this conventional example 1 displays fixed colors such as black on a display screen only for a predetermined period and displays images free of disturbance when the video signals and sync signals of the target signal source become stable.
Then, conventional example 2, which is a technology to reduce disturbance of images displayed and is different from conventional example 1 will be explained. This conventional example 2 uses a sync signal common to all signal sources by supplying a sync signal output from one signal source to other signal sources. Thus, conventional example 2 can eliminate discrepancies between sync signals during a changeover and thereby reduce disturbance of images displayed.
However, conventional examples 1 and 2 have the following problems. That is, conventional example 1 displays images in a single color during a changeover, giving the user an unpleasant impression. Conventional example 2 always needs to operate the signal source to supply sync signals even when a video signal output from another signal source is displayed, having a problem of increasing power consumption.